Eddy Current Testing using an axial probe

Positioning of AVB bars using Eddy Currents

Background

The MHI contract to supply replacement steam generators (SG) to EDF includes the requirement to justify that the anti-vibrations bars (AVB) placed to support the SG tubes in the upper region are positioned in compliance to specifications.

The objective of this service is to ensure that all the rows of tubes are correctly maintained up to levels 2 and 9, depending on the type of AVB. To do this, a schedule has been defined with MHI to inspect all the tubes in rows 2 and 9.

Service provided

The preconized method to do this in compliance with EDF requirements is based on a technique using Eddy Currents (ECT).

The operation involves displacing an axial probe along the interior of the tube using an integrated all-in-one system (including frequency generator and push-pull device) - the MIZ81 Zetec.

A carrier robot is introduced inside the SG channel head and fixed on the tube plate. It allows to move the probe from one tube to another.

The entire inspection sequence is computer-operated, using the software suite Eddynet /Zetec.

After recording the EC signatures of each tube, data analysis enables to confirm the presence of AVB ( by signal detection and amplitude/phase measures).

An alignment reference standard is installed between the push-pull device and the carrier. It enables to calibrate the alignment of the EC signals